ParseEnvisatLevel0ImPackets: asar_meta.swath_idx initialized too late

[aha66]

asar_meta.swath_idx initialized here:

asar-focus/envisat_format/src/envisat_im_parse.cc

Line 973 in 446cea5

asar_meta.swath_idx = swath_idx;

but used already here:

asar-focus/envisat_format/src/envisat_lvl0_parser.cc

Line 199 in 446cea5

const float az_bw = con_file.tot_azimuth_bandw_ims[asar_meta.swath_idx];